Diocletian

Diocletian (244-311) was Roman emperor from 284 to 305, succeeding Carinus and preceding Maximian.

Biography
Gaius Aurelius Valerius Diocletianus was born in 244 AD in Salona, Dalmatia, Roman Empire (present-day Solin, Croatia) to a family of low military status. He rose in the ranks of the Roman military and was appointed the head of Roman emperor Numerian's bodyguards in Roman Syria. When Numerian died at Emesa (Homs, Syria), Diocletian claimed that he had been murdered, and Numerian's partisans acclaimed Diocletian as emperor. Diocletian led an army to Moesia to meet that of Numerian's brother, Carinus, who had been proclaimed emperor in the west. In the Battle of the Margus, Carinus' army was completely defeated, and he became emperor when Carinus was assassinated. In 286, he made Maximian his co-emperor, and on 1 March 293 he created the "tetrarchy" to divide the empire between four men, appointing Galerius and Constantius as co-emperors as well. Diocletian secured the borders of the empire, fighting the Carpi and Sarmatians from 285 to 299, the Alemanni in 288, and defeating usurpers in Egypt in 297 and 298. He also assisted Galerius in fighting the Sassanids, sacking their capital of Ctesiphon. On 1 May 305, Diocletian decided to abdicate, but not before instituting a terrible persecution of Christianity in 303, which would continue until 311. He retired to a palace near present-day Split, Croatia, where he died in 311.